Heretofore numerous efforts have been made to improve the operation of a rotary tool, such as for example a rotary end mill tool holder to improve the accuracy of the rotating tool during a machining operation. In many cases, such for example as disclosed in U.S. Pat. Nos. 5,033,923 and 5,125,777 a rotary tool holder has been provided with a plurality of axially extending, internally threaded openings, which are equi-angularly spaced about the axis of the rotary tool holder, and which extend parallel to the axis of the holder. To help maintain uniform rotation of the holder coaxially about its axial centerline, each of the internally threaded openings has removably mounted therein a balancing weight, such as a screw, or the like. Such screws, which are equi-angularly spaced from each other about the axis, are removable and replaceable to stabilize the rotation of the holder during its operation.
A variation of this type of tool holder can be found in U.S. Pat. No. 5,096,345, wherein the tool holder is provided with a plurality of internally threaded openings which are equi-angularly spaced from each other about the axis of the holder, and the axial centerlines of which intersects the axial centerline of the tool holder at equal angles. The tool holder is balanced, not by inserting or removing the screws, but merely by adjusting each screw axially in its associated, internally threaded bore, so that the centrifugal force applied to the tool during its operation can be satisfactorily balanced.
When the above-noted tool holders are to be used, a tool is inserted in the appropriate holder and the assembly is then mounted in a conventional balancing machine which is utilized to detect any undesirable vibration introduced into the tool by virtue of the fact that the tool is unbalanced during rotation. The above-noted weights or screws in the cases of the first two above-noted patents are then inserted or removed until the combined tool and holder are properly balanced. In the case of the third patent, this proper balance is achieved simply by adjusting the screws axially in their respective internally threaded bores.
Among the disadvantages of prior art tool holders of the type noted above is the difficulty in accurately balancing the combined holder and tool assembly, particularly in the case of the U.S. Pat. Nos. 5,125,777 and 5,096,345, since the weights in the associated screw holes must be removed and or replaced by different weights until the desired balance has been achieved. In the case of the U.S. Pat. No. 5,096,345, the screw holes for retaining adjustable weights must have the axes thereof carefully directed to intersect the axial centerline of the holder at a predetermined given angle for each opening.
It is an object of this invention, therefore, to provide an improved, balanceable tool holder which employs a plurality of adjustable weights that are mounted adjustably in internally threaded screw openings that are formed in the outer peripheral surface of the tool holder at circumferentially spaced points about its outer peripheral surface, and which openings have the axes thereof extending tangentially with respect to the axial bore in the tool holder. In this way the weights are readily adjustable axially within their respective openings, and are readily accessible as compared to prior art tool holders of the type described above.
Still another object of this invention is to provide an improved tool holder of the type described in which a plurality of balancing weights are adjustable in internally threaded openings that extend substantially tangentially of the bore of the tool holder and which weights are readily adjustable axially of their respective openings.
Still other objects of this invention will be apparent hereinafter from the specification and from the recital of the appended claims, particularly when read in conjunction with the accompanying drawings.